Electrical discharge device



July 19, 1927;

w. H. T. HOLDEN ELECTRICAL DISCHARGE DEVICE Fil ed April 10, 1922INVENTOR. W .flZfiwa W BY way? A TTORNEY.

Patented July 19, 1921.

UNITED STATES mm H. '1. -HOLDEN, OF NEW YORK, H. Y.,

ASSIGNOB T0 AMERICAN mmon m maemn COMPANY, A CORPORATION O! NEW YORK.

ELECTRICAL DI CHARGE DEVICE.

' Application fled April 10, 1929. Serial Io. 551M8.-

This invention relates broadly to electrical discharge devices andparticularly to an electric lamp designed for signaling purposes, as,for example, in telephone switchboards.

Electric lamps based upon the principle of discharge between coldelectrodes in a glass envelope or bulb filled with an inert gas such asneon, helium, argon. etc., are well known to those familiar with theart. Such lamps are in general made by two processes-one which may bedesignated the allglass process, and the other designated as amodification of the ordinary bench-exhaust system.

In the all-glass process, the glass bulbs into which the electrodes havebeen sealed are welded to the glass tubes to which are also connected avacuum pump and a container of the inert gas with which the lamp bulbsare to be filled. After the air has been exhausted from the lamp bulb bymeans of the air pump connected with the glass tubes of the all-glasssystem, the pumping is discontinued and gas is allowed to flow throughthe said tubes from the gas container into the lamp bulbs, until thesaid bulbs are filled. with gas at the desired pressure. The lamp bulbis then sealed oil. in a manner well known in the art of manufacture ofglass lamps. It will be seen that in such a process, if the lamp bulbhas been carefully welded to the tubes of the all-glass system, air willnot enter the bulb after the pumping has been discontinued and duringthe time of filling the bulb with the inert gas. This process results inlamps of high quality, but, as will be apparent, it is costly ofoperation in view of the time necessary to seal each of the individuallamp bulbs to the glass tubes of the all-glass system. In addition, themaintenance cost of the all-glass system is expensive, and furthermore,there is always present the possible loss of the expensive gas throughaccidental breakage of the system.

The second process, utilizing the usual brass manifold and piping,joined by rubber tubing, is designed to reduce the ,.cost of productionof such lamps by eliminating the, step of welding the glass bulbs to theall-glass system. In the second process, the individual bulbs which areto be exhausted and filled with the inert gas, are attached to the brassexhaust manifold by means of a discharge takes flexible rubberconnection, which readily permits of the replacements of the lamp bulbsafter the preceding exhausted ones have been sealed ofl. e glass neoncontainer and sultable glass stopcocks are joined to the manifoldthrough a rubber connection, and this, the only glass part of thesystem, can be readlly protected from breakage. It will be seen thatvarying degree of leakage around such rubber connections, so that afterthe pumpin ceases, air mixes with the inert gas wit which the lamp bulbsare filled.

The presence of residual air in suchbulbs prevents the operation of thelamp at the desired voltage, and it is important to provide means foreliminating it. Various means are provided for efiecting the desiredresult. ne of these consists in giving the lamp, after it has beensealed off, a so-called seasomng or flashing treatment which vaporizes asuitable chemical called a getter, which removes the impurities in thegas by forming compounds of very low vapor pressure. These, compoundsare deposited mainly on the walls of the lamp and leave the inert gas ina condition of high purity. Various elements have been used as a getter,such for example, as metallic magnesium or calcium, which is spot-weldedto one or both of the electrodes. A high potential is then applied tothe electrodes, and a place from the getter to the other electrode,"because of the lower cathode fall between the getter and the surroundinggas. The combination of the getter with the oxygen and the other activeelements of the air results in a grayblack, silvery, the glass bulb,which renders such lamps unsatisfactory, if ,not, useless. In certainforms of lamps, such for example, as those used in spark-plug testingdevices, the electrodes are placed in opposite'ends of a relatively longtube, the central portion of which 1s considerably attenuated. This, inefiect,

confines the cloudydeposit to the ends of the.

tube, and leaves the central portion clear, so

in such a system there is a or almost opaque depositv on that thedischarge through the inert gas,

which occurs in normal operation, maiy be s of readily observed throughthe glass wal the central part of the tube. This method can not becarried out in lamps which are designed to operate at relatively lowvoltage,

produce a lamp operating upon -walls of the said lamp such for example,as the ringing voltage used with telep one signaling es, becausecharacter described, in which one of t e electrodes substantiallysurrounds the other electrode, so that the discharge between the saidelectrodes takes place in a region almost entirely surroun-de by metal,whereby the absorption of the inert gas by'the glass walls is less thanin 1am s where the discharge is near the glass wal s of the bulb,thereby increasing the life of such lamps.

A further object of my invention is to provide a lame for use insignaling as, for example, in telephone switchboards, in which thedesired color of the lamp may be produced by the electrical dischargethrough a selected inert gas which produces a glow having thedistinctive color desired. I

This invention will be better understood from the followingdescription,when read in connection with the attached drawing, of which Figure 1shows a longitudinal cross section of a preferred form of embodiment ofmy invention; Fig. 1' shows an end view of thesame; Fig. 2 shows alongitudinal cross section of an alternative form of the invention, andFig. 2, an end view of Fig. 2.

In Fig. 1, 1 represents the glass bulb or receptacle into which havebeen laced and sealed the connecting wires 2 an 3, which are connectedwithin the bulb with the electrodes 4 and 5. The leading-in wires 2 and3 are held together by means of a glass head '6, which tendstostrengthen the structure,

and also tends to prevent the discharge from taking place elsewhere thanbetween the electrodes 4 and 5. The electrode 4 may be of the form of asolid cylinder or any other suitable form. The electrode 5 consists of ahollow cylinder which preferably is designed to entirely surround theelectrode 4, thereby confining the discharge substantially to the spacebetween the two electrodes. Attached to the electrode 4, by welding orother suitable means, is a iece of magnesium, calcium, or other suitab ematerial, designated as the getter, the flmction of which is to removethe active elements of air that may be present in the bulb after it hasbeen sealed off. When the lamp has been sealed off, after being filledwith the inert gas, which, as heretofore stated, may contain a certainamount of air due to leakage of the system, or to any other cause,thewires 2 and 3 are connected with a source of high potential and adischarge takes place between the getter 7 and the other electrode,which, in the case of the lamp shown in Fig. 1, is the cylinder 5. Whenthe dis" charge takes la'ce the getter vaporizes and combines wit theactiveelements of the air, such as oxygen, nitro 11, etc., formingcertain compounds, whic presence of the cylindrical electrode 5 would bedeposited on the inner'surface of.

the bulb 1, thereb 'discoloring the bulb. However, due to t e presenceof the cold cylindrical electrode around the other electrode, to whichthe getter is attached, the compounds formed b the union of the getterwith the said e ements of the air, are deposited upon the inner surfaceof the c lindrical electrode 5, thereby keeping t e walls of the bulb 1substantially free from any deposit. After the getter has beenvaporized, the electricaldischarge through the inert gas will take placebetween the electrode 4 and the cylindrical electrode 5. This discharge,when viewed from the end of the lamp, as shown in'Fig. 1, will appear asa glow within the cylinder 5. Although the area of a cross-sectionthrough which the discharge takes place, as shown in Fig.1, is not verylarge, the glow is (guite intense, due to the depth of the cylin er 5,thereby rendering this type of lamp readily adapted for such use, as intelephone switchboards, where only the end of the lamp, as shown in Fi1, is visible. It will be seen, therefore, 51211, by means of myinvention, a lamp ma be produced in which the walls are not arkened, orotherwise similarly afiected, so that the emission of light from the endof the bulb is notobscured, and also in which the electrodes may beplaced sufliciently close together to e operated, for example, by thenormal ringing potential of 110 volts, or other low voltage.

A further advantage of the construction,

in which the outer electrode is a concentric cylinder surrounding theother electrode is that the discharge takes place in a region almostentirely surrounded by metal, so that the absorption of the inert gas bythe glass walls of the bulb is much less than in lamps heretoforedesigned, in which the discharge takes place near the glass walls,thereby prolongin the life of the lamp.

Another form of the lamp is shown in lon-' gitudinal cross-section inFig. 2, an end view of which is shown in Fig. 2". In these figures,parts similar to those in the foregoing figures have been given the samedesignating numerals. The arrangement shown in Fig.

2 diifers from that shown in Fig. 1 in that were'it not for the.

1,oao,ou Y t in Fig. 1, as for example, cheapnciss of production,- it isnot believed to be as desirable a form as that shownin Fig. 1, becausethe compounds resulting from the combination of the getter with the aircan pass through the spaces between the adjacent convolutions of thehelix, and reach the inner walls of the glass bulb. It will be apparent,however, that if the getter tit-y and is localized at a point near themiddle ot' the inner electrode, the end of the bulb will still beprotected against the emission from the getter, so that we get theresult that is desired in atelephone switchboard lamp, namely, clearnessof the end wall, and the concentration of the discharge through theinert gas between the two electrodes, which tends to diminishabsorption.

Another feature of my invention consists n the utilization, in a lampintended, for exam le, to be used in telephone switchboard of variousinert gases, either singly or in combination, in order to produce glowsof different colors, thereby serving the same function which is nowperformed by a switchboard lamp of the incandescent type, covered by acolored lamp cap. Thus, for example, by using neon as the inert gas, alamp producing a reddish glow may be ob tained. By the addition of atrace of mercury, a bluish glow may be produced in lamps of this type.The use of argon or helium as the inert gas produces a blue or ayellow-white glow, respectively. Accordingly it is practicable to obtaina fairly wide range of colors or shades of color by usin various inertgases in lamps of the electrical disc large type which are intended forsignaling purposes, such as in telephone switchboards. Although the factthat certain inert gases produce characteristic colors of glow inelectrical discharge devices is probably old, I claim as a new inventionthe application of the principle in a novel way to produce a new anduseful result not heretofore contemplated or disclosed in the art. Bythe use of such lamps it is possible to supplant not only theclear-glass incandesa lamp of the desired cent lamps with their coloredlamp-caps, but also lamps in which the coloring material is worked intothe walls of. the glass bulb, both of which forms of lamps wereexpensive and of low lighting efiiciency.

It will be seen, therefore, that in accordance with the principles of myinvention, a color may be produced which is well adapted for use insignaling service, such, for example, as in telephone switchboards,which can be manufactured more cheaply than the present incandescentlamp, which performs the same function as is now performed by such alamp and its colored lamp cap, which is adapted to operate at the normalsignalin potential now used, and which is free from %he discoloration isnot too large in quanwhich heretofore characterized gas-filled lampspreviously used.

A though this invention has been disclosed as being embodied in acertain form and arrangement of parts, it is to be understood that it iscapable of embodiment in other and different forms without departingfrom the spirit and scope of the appended claims.

What is claimed is:

1. In a lamp characterized by the discharge of electricity throughgases, the combination with a transparent gas-tight envelope filled withinert gas and having an active gas also present, of a pluralit ofnormally cold electrodes, and means a xed to one of. the said electrodesand activated by the discharge between the said electrodes to change thesaid active gas to inactive chemical combinations, one of the saidelectrodes substantially surrounding the other electrode tosubstantially prevent discoloration of the transparent envelope by thesaid chemical combinations.

2. In a lamp characterized by the discharge of electricity throughgases, the combination with a transparent gas-tight envelope containingneon gas at a predetermined pressure and having a trace of air present,of two normally cold electrodes, and a means associated with saidelectrodes to roduce a chemical change upon the contained air, one ofthe said electrodes substantially surrounding theother as toefi'ectually shield the said envelope against the products of the saidchemical combination, whereby clouding of the walls of the envelope isprevented.

3. In a device characterized by the discharge of electricity throughgases, the combination with a gas-tight envelope, a part of i which atleast is transparent, containing inert and active gases, of a pluralityof electrodes one of which effectively surrounds the other, a getter,interposed between the said electrodes and activated by the dischargetherebetween to substantially prevent the deposit upon the transparentpart of the envelope of compounds formed by the get-tier with the saidactive gas.

4.1m a lamp characterized by the discharge of electricity through gases,the combination with a transparent gas-tight envelope containing inertgas and an active gas at a predetermined pressure, of a plurality ofcold electrodes, and means activated by the discharge between the saidelectrodes to change the active gas into inactive chemical compounds,the said envelope being protected by one of the said electrodes againstdiscoloration resulting from the discharge between the electrodes.

' In testimony whereof, I have signed my name to this specification this8th day of April, 1922.

WILLIAM H. T. HOLDEN.

